Taking a moment to shamelessly ignore how quiet it has been here for a while now, I just discovered that the musical score played during the boss fight against Ludwig the Accursed actually have [url=https://bloodborne.fandom.com/wiki/Ludwig,_the_Holy_Blade_(OST)]lyrics[/url] in Latin. I've found some different claims, but the wiki page I just linked to seems to have a fairly decent translation of what the lyrics would be:

[HIDER=Lyrics from Ludwig's theme]
Oh, hunter.

Blessed saint.

An honest death is like a blessing.

Let death come once and for all.

Plenteous blood is lost

Mutated into an unsightly beast

Mutated a long, long time ago

Still, as a mentor, I always were at your side

Even when you had turned into a beast

The master of the hunters, who stood guard in the night with his moonlight

The first hunter who organised the folks to hunt

The first hunter of blood

And one of the first who mutated into vile beasts by the blood

You turned into a beast.

Oh, hunter.

That Saint.

The Divine Partner of your fate

May it come by mean of the Death, the Departed(or Missing) Blame (or Pain)

The Blood will flow in abundant 
[/HIDER]